Determination of free alkali content in detergent

The REX Ti-50 Automatic Potential Titrator allows quick and simple determinations of the free alkali content of detergent. 

The alkalinity or acidity determined using phenolphthalein as indicator, expressed as the "alkali value" or the "acid value" as the case may be, i.e. in milligrams of potassium hydroxide present in 1 g of the product or required to neutralize 1 g of the product.

Alkalis such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) are usually used in the production of detergent. In an ideal production process, the alkali reacts completely with fatty acids and saponification is complete. However, due to production errors or unbalanced formulations, a small amount of free alkali may remain in the detergent.

Free alkali: Alkaline components that are not fully saponified.

Total alkali: The sum of the free alkali and other unsaponified alkali compounds in the soap.

A high total alkali/free alkali content can cause the soap to cause skin irriation or sensitization.

1. Standard Reference

ISO 4314:1977 Surface active agents — Determination of free alkalinity or free acidity — Titrimetric method

ГОСТ 32439-2013Товары бытовой химии. Метод определения щелочных компонентов 

GB/T 13173-201 Surface active agents——Test methods for detergents

2.  The Principle

ISO 4314:1977: Titration of an ethanolic or propanolic solution of theproduct with a standard volumetric potassium hydroxideor hydrochloric acid, in the presence of phenolphthalein asindicator.

3. Recommended Configuration

1. Ti-50 Automatic Potential Titrator 

• Range：(-2000.00~2000.00) mV
• mV Accuracy：±0.03% or ±0.2mV
• 1 extra burette driver can be installed (optional).
• Replaceable burette with high-accuracy (10 ml or 20 ml selectable).
• Support acid-base titration, non-aqueous aqueous phase titration, constant titration, REDOX titration, precipitation titration, complexation titration
• Support the following titration modes: DET (dynamic equivalence point titration), MET (monotone equivalence point titration), SET (Preset Endpoint Titration) and MAT (manual titration).
• Titration methods, curves and results are displayed in detail

      

      2.  Anti-diffusion capillary

      3.  Electrodes：982211 Non Aqueous pH Titration Electrode

Model	982211
Name	Non aqueous pH titration electrode
Connector Type	S7
Sensor material	Glass
Dimension	Φ12×120mm
Measuring unit material	Glass
Working Temperature	0-60℃
Application	Non aqueous acid-base Titration

 

 

4.Procedure:

• Weigh, to the nearest 0,001 g, about 10 g of the laboratory sample into the conical flask.
• Add 100 ml of the ethanol or the propan-2-01 and shake to dissolve the test portion  completely.
• Add 4 to 5 drops of the phenolphthalein solution.
• If the solution is pink, titrate in the same manner with either the 0.1mol/L hydrochloric acid or sulphuric acid solution.
• Titrate directly with 0.1mol/L hydrochloric acid or sulphuric acid solution to a single exothermic endpoint.

5.Titration Setting

• non-aqueous aqueous phase titration
• Sample: DET (dynamic equivalence point titration)